JZ4720 provides internal CODEC is an I2S/AC97 audio CODEC with 18 bits DAC and 16 bits ADC. The audio system of this design makes use of the internal CODEC to implement the input and output of audio. It consists of MIC­in with two solder pastes MIC+1 and MIC­-1, headphone jack J3, an amplifier U10 GPY0030B for external speaker connecting to the solder paste SP+1 and SP­1. When plug a headphone in J3, the amplifier will be off. The audio system provides record with gain control; stereo headphone output with bass/treble boost, and output volume control by software.

There are 58 keys reserved by software control. An another ON/OFF key S9 connected to pin 124 WAKEUP_/PD29 of jz4720. A reset key S1 connected to pin 123 PPRST_ of jz4720. When this pin receives Low, the cpu will start a reset procedure.

The schematic can be downloaded qi_avt2_v1.0.pdf. All the data sheets of the related parts on this board you can found here. If wants to understand how this open left hardware board working, you can also check our Hardware basics for some basis of hardware involved in NanoNote. If you are interested in waveforms of schematics inside. You can check avt2 waveform page for your help. Be aware of each waveform's duration measured. Their duration which some of them by hardware itself not software control to cause it. Some of them are depended by your software porting. Just see every description of each, then you can check it out. Since avt2 is very likely to Ben NanoNote excepts USB host, you can also see Ben NanoNote's waveform page.